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Power System Small Signal Stability Analysis Including Wind Farm

Posted on:2011-08-30Degree:MasterType:Thesis
Country:ChinaCandidate:G H LiFull Text:PDF
GTID:2192360305471608Subject:Power system and its automation
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Small-signal stability is not only an important content for power system to maintain secure and stable, but also a key factor in power system interconnection. Meanwhile, wind power takes up higher and higher percentage owning to its unique advantages of no pollution, abundance in reserve, reproducibility, which brings a new subject to small signal stability and damping characteristic analysis on power system with wind power integration. In this paper, oscillation modes of a simple system with wind power are analyzed, on the basis of which small signal stability of power system with wind power integration is studied. Its main contents are as follows:(1) Linearized models suitable for small signal stability analysis of mechanical system in wind turbine generator are established, including wind turbine model, shafting model and pitch angle control model. Dynamic equations of asynchronous generator and doubly-fed induction generator (DFIG) are established. Linearized status-equations of converters and the controlling system are established.(2) Models of single machine-infinite bus system based on asynchronous generator and DFIG are established, and then oscillation modes and the relationship between modes and state variables are calculated, and the results demonstrate that there are oscillation modes and damping modes in both systems, and the damping ratio of oscillation modes are of good performance, the results also demonstrate that the determining factors are different in both conditions. For the system based on asynchronous generator, the changes of oscillation modes and damping ratio were studied in the condition that output of wind turbine generator and outer reactance change. The results demonstrate that the state variables most relevant to oscillation modes are q-component of transient potential and slip, furthermore, no obvious changes occur in oscillation frequency and damping ratio, that is to say, the above two factors have little impact on the small signal stability. While, for the system based on DFIG, low frequency oscillation modes are decided by d-component of transient potential and slip; the state variables most relevant to the higher frequency oscillation modes are transient potential, stator active power error, voltage error; control system of converters have decisive effect on the oscillation modes of the highest frequency, which means that low frequency oscillation of power system based on DFIG are mainly determined by rotor movement and transient potential.(3) On the basis of above analysis, a system with 3 generators is taken as a research object, and small signal stability is analyzed considering the location and output of wind turbine generator. The results show that the output has larger impact on oscillation modes than the location; moreover, the inter-area modes are more apt to be affected than local modes. In both systems, the oscillation frequency has no obvious change, and the location has almost no impact on the oscillation modes and damping ratio. For the system with asynchronous generator, all damping ratios are increased, while for the system with DFIQ the truth is just the reverse. That is to say within a certain range, the larger the wind turbine generator output is, the more beneficial to small signal stability for the system with asynchronous generator, but the reverse for the system with DFIG.(4) The measure of increasing the parallel capacity is adopted based on all work above. The results demonstrate that after the measure is adopted, the damping ratio of inter-area oscillation modes are increased, that is to say, the measure is beneficial to the power system small signal stability.
Keywords/Search Tags:wind farm, small signal stability, damping characteristics, inter-area oscillation, MATLAB
PDF Full Text Request
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